In the Powder Metallurgy industry (PM industry), metal powders, such as iron-based powders, are used for production of components. More particularly, metal powder compositions are compacted in a die under high pressure into green compacts, the green compacts are then ejected from the die and sintered into sintered compacts. This near net shape technology enables the production of parts at a lower cost than other conventional methods such as machining.
The metal powder composition comprises a mixture of metal powders, lubricant, and, optionally, other additives. The powder metallurgy lubricants are generally different types of waxes, which are either ground or atomized into fine particles, and blended with metal powders, such as iron and steel powders. The lubricant reduces the inter-particular friction and the friction with the die wall during compaction and therefore improves densification, but also reduces friction with the die wall during the ejection of the part from the die. Furthermore, the lubricant is selected to promote the metal powder composition to flow adequately within the die cavity and also be malleable enough not to hinder the compaction process. There is a strong relationship between the mechanical properties and the final density of the parts. Consequently, lubricants which allow for higher densities to be attained have additional value. Commonly used lubricants for PM applications comprise metal stearates and amide waxes such as ethylene bisstearamide wax. Albeit being excellent lubricants, metal stearates can stain the parts during sintering and cause heavy metal contamination through the sintering furnace exhaust fumes.